Can ReSharper 7.x be used with VS2013 preview?
Can ReSharper 7.x be configured to work with Visual Studio 2013 preview?
The preview version doesn't appear to allow it by default - though I only tested by repairing ReSharper, rather than uninstalling/reinstalling.
I'm aware that ReSharper 8 is on its way and may be a better long term option.
Being able to evaluate a new IDE under the same conditions that I use VS2012 is imperative, so this would help massively in that goal.
UPDATE
It looks like the answer to this is that it cannot be used - the accepted answer demonstrates a possible, untested method of wiring it up but there are now 3 or 4 cases where the solution has not worked, including an attempt by myself to hook it up which unfortunately didn't work. As such, I've added this update to avoid misleading anybody who comes across this.
Answer
Warning: This has only been tried by me just now on VS2013 with the latest v8 EAP, this may cause crashes or slowdowns etc and I can't say how v7 would behave.
If you go into your program files folder, then open the VS2012 folder, navigate to Microsoft Visual Studio 11.0\Common7\IDE\Extensions .
From that folder grab the Jetbrains folder, and copy and paste it to the same location but substitute 11.0 for 12.0.
Then open the file inside the Jetbrains folder named extension.vsixmanifest in any text editor of choice (remember about running as admin) then inside find where at the top on approx lines 11 - 16 , you will have a section named VisualStudio.
Copy and paste this whole block and paste it again below (inside the SupportedProducts section still).
Edit the Version="11.0" to Version="12.0" and then save the file, re-launch VS2013 & you should now end up with resharper working.
Nice and simple :) Also for future reference this technique works on any extension, also some extensions are stored in AppData instead. Just thought I'd reply with this to make sure you got a helpful reply :D